Personally I love the 4890, I don't know what the performance comparison is but I bet its close which may not warrant the upgrade. If you do upgrade go with the ASUS so you can change the voltage without re-flashing.

I can max out the default upper limits on the setting and still run stable at 1.375v

If your current card is giving you decent, playable frame rates, don't bother with either. If you must spend the money - get the best deal at the moment (the HD 4890). Just like the GTX 260/HD 4870 debate before them, there's almost no difference between the two performance wise.

If your current card is giving you decent, playable frame rates, don't bother with either. If you must spend the money - get the best deal at the moment (the HD 4890). Just like the GTX 260/HD 4870 debate before them, there's almost no difference between the two performance wise.

Hello British friends...
Buy the 4890, great overclocker.
Maxes out all settings in Farcry2 and Crysis. And yes, 8AA. Mine is overclocked @ 1Ghz core and 1150 (4600) Memory. Vcore set to 1.375. Can't achieve over 1150 on the memory. I guess some cards may have received slightly faster memory chips. Different date code, lot, who knows.